Many embodiments of diapers, sanitary napkins and catamenial tampons and similar absorption bodies are known. However, no known construction is particularly suitable for female urinary incontinence, which poses certain quite special demands. The absorption body must be flat, have a modest thickness in the dry condition and have a suitable width. It must be fairly uniform in its entire length and width, first so as to not require the exertion of a high degree of precision at its application and secondly so as to cause no harm if displaced while being worn by the user, such displacement being almost inevitable.
A particularly important requirement is that the absorption body is able to absorb very rapidly a significant amount of urine. In cases of female urinary incontinence it frequently happens that in a vigorous flow (15-25 ml/sec.) urine flows out for, e.g., 1/2 to several seconds. These amounts of urine should be subject to immediate absorption and avoid overflow. A total absorption capacity in the absorption body of for instance 70 ml in a number of cases may be considered sufficient, but for some disorders it must be greater. An absorption body for the main purpose stated thus must have properties different from those of sanitary napkins which are to absorb a fluid flowing more constantly and slowly and having a much higher viscosity than urine.
It is known to manufacture absorption bodies with a receiving chamber from which urine may be distributed into the core of the absorption body. This has been found, however, to involve the drawback that the urine may have difficulties in being distributed into the entire core because the parts thereof bordering on the receiving chamber are rapidly saturated with a corresponding reduction of through-flow. In these cases, conventional sanitary napkins have a tendency to press out the urine when compressed from urine absorption.
It will be understood that an absorption body for the present particular purpose must have a series of properties. One of them is that the above-mentioned receiving chamber is replaced by a number of channels--preferably rectilinear and parallel--in the core body responsible for the absorption of the urine.
From DK patent specification No. 122,636 there is known a diaper of a highly absorbent material, preferably dry-fibered cellulose, having several depressions (which may be rectilinear and largely parallel). The depressions have been made by compression. The considerable disadvantage in such an absorption body arises because the compression will slow down somewhat the rate of the absorption of fluid and thereby render the diaper unsuitable for the absorption of such vigorous flow of urine generally experienced in the case of incontinence.
From the German published specification No. 2 319 309, which is mainly concerned with the kind of absorbing material (CMC-derivatives), it is known to provide a core with longitudinal, parallel depressions. It appears that the material is formed by embossing, i.e. compression, and thereby have the above-mentioned drawback in relation to an absorption body with the purpose here aimed at.
From U.S. Pat. No. 3,343,543, Glassman, there is known a sanitary napkin provided with troughs for the absorption of liquid. These troughs normally have been formed by compression with similar drawbacks described above. However, it is also stated that the napkins may be formed by cutting although there is no explanation how or for what purpose. Glassman also represents that one or more layers of wrinkled or grooved paper may be present in the body of the napkin between its upper and lower faces to retard the flow of fluid to the bottom region thereof. The purpose of these layers is to ensure total absorption by the upper region of the napkin before a material quantity of the fluid reaches and is absorbed by the lower portion. As such, with this absorbing object one does not attempt to obtain the fastest possible rate of the absorption of fluid. Presumably this is connected with the fluid characteristics, i.e. higher viscosity of the material to be absorbed and perhaps also with the fact that it comes in a relatively slow flow.
From U.S. Pat. No. 3,411,504, there is known a sanitary napkin in which the surface facing the source of fluid is provided with a ridge situated between two grooves, the ridge being adapted to fit in between labiae majorae in order to ensure against leakage. The grooves are preferably formed by compression, that method being stated to increase the absorption capacity. Such an absorbing object is not suitable for the purpose of the present invention, i.e. because there are precisely only two grooves and the object therefore cannot absorb uniformly and evenly over its entire surface.